During mitosis in most eucaryotes, the processes of secretion, receptor mediated endocytosis, and receptor recycling come to a halt. The most striking alteration in the intracellular organization of mitotic cells is the loss of the nuclear envelope (NE) and the assembly of the mitotic spindle. The role of the nuclear envelope in intracellular trafficking of membrane glycoproteins and a cytoplasmic proteins is under investigation. Using a temperature sensitive mutant of Vesicular Stomatitis Virus (VSV), it is possible to study the assembly of the single glycoprotein of the virus in a synchronous fashion. The mutant protein accumulates in the Rough Endoplasmic Reticulum (RER) and Nuclear envelope (NE) as the non-permissive temperature. Using developed procedures for cell anucleation, functional nucllei containing the G protein can be removed from an infected cell and reinserted into a foreign cell. Retaining the cells to the permissive temperature to induce secretion will allow a determination of the extent of communication between the Nuclear envelope, Rough endoplasmic reticulum and other organeles. The primary sequence information required for passage through the nuclear pores into the nucleaus have recently been defined for the Large T-antigen of the virus SV-40. Synthetic peptides composed of this sequence are being used as probes, to identify nuclear envelope components involved in translocation to the nuclear interior.